In one conventionally known ship (shaft ship), power is transmitted from an engine, provided in a ship body, to a forward/backward propeller, provided outside the ship body, via a switching clutch and a propeller shaft. Furthermore, in another known ship, a side thruster is provided for causing the ship to laterally move left or right to achieve higher operability at the time of docking or the like. The side thruster includes a propeller provided around the center of a bow side in a left and right direction so that thrust is generated in the left and right direction. Thus, the ship is configured to be laterally movable by the side thruster, whereby a docking operation can be easily performed.
When the ship with such a configuration moves in a desired direction, a rotation moment acts on the ship due to a relationship between a position of the ship corresponding to the center of gravity and thrust generated by the side thruster. Thus, the ship makes a lateral movement with the ship handling device performing rotation correction with the thrust generated by the side thruster and thrust generated by the forward/backward propeller, as well as correction thrust generated by the forward/backward propeller. Thus, the ship handling device controls the movement of the ship by controlling each of the side thruster and the forward/backward propeller (engine). This is described in Patent Literature 1 for example.
The ship handling device described in Patent Literature 1 is required to change a control mode for moving the ship in the desired direction, in accordance with the position of the side thruster with respect to the center of gravity position of the ship, the shape of a ship body, and the like. Thus, the relationship between the thrust generated by the side thruster and the thrust generated by the forward/backward propeller does not hold true in a ship that does not correspond to the condition of the experiment and the calculation for determining the control mode or when the side thruster and the forward/backward propeller are provided at unexpected positions. In such a case, an operator needs to control each of the thrust generated by the side thruster and the thrust generated by the forward/backward propeller.